The
432MHz band used to be one of my favourites.
In the early 1980s I owned one of the first FM321 70cms synthesised
4W FM transceivers (based on an Australian CB radio) and with
this and an old Jaybeam 48el TV antenna mounted vertically on
a pole and turned by hand on the side of the house I was able
to work lots of local repeaters and some decent inter-G DX on
FM simplex when there was "a bit of a lift on". 70cms has localised lifts every few days and that was
part of the magic of the band: one day you could hear just locals
and the next (in just one direction maybe) more distant repeaters or
simplex stations could be heard or worked. Every day was different.
Occasionally the band would be wide open and some super DX could
be heard or worked.

In those days I did not have
any SSB transmitting gear on the band but I did listen in contests
and at other times and well recall hearing an OZ station running
10W to an HB9CV antenna and being a true 59+ signal on a small
indoor beam in the bedroom. The band is excellent for tropo
DXing but it is much under-used nowadays.

Fortunately there is still
activity during contests and on Aug 3rd 2008 there was the RSGB
70cms low power contest restricted to stations running 25W or
less. For a change I wanted to have a go /P but the problem
was I had no beam antennas for the band just a the vertical
colinear fixed on the side of the house. So, a check on the
net showed up a design for a Moxon 2el yagi using a coat
hanger! A quick search through my wife's wardrobe turned up
a suitable metal one and 30 minutes of relaxing sawing, bending and straightening
in the back of the garage resulted in a somewhat "Heath Robinson"
2 element antenna attached on the end of a 2m long plastic conduit tube.
Connection between the coax and the feedpoint was via a small
terminal block and the insulator between director and driven
elements by a piece of PVC insulation grabbed from some 2 core
cable. The whole antenna was supported on the pole using a support
bracket made from a remaining piece of the coat hanger.

The Moxon 2el Antenna

The Moxon antenna was designed
by Les Moxon G6XN and is an optimisation of an earlier Australian
design for a compact 2el beam. Essentially it consists of two
metal or wire elements: (1) a driven element with its ends
bent back towards the reflector (2) which has its ends
bent towards the driven element. The entire antenna therefore
forms a rectangle but occupying a space much smaller than a
corresponding unbent 2el beam sucj as the HB9CV.

The antenna is broadband,
has a broad (100 degrees) front lobe, a good front-to-back
ratio and a useful amount of forward gain and presents a decent
near 50 ohm match at resonance. On HF these properties
allow a small, lightweight beam to be erected with excellent
performance for the size. On VHF/UHF it allows a smaller alternative
to the popular HB9CV antenna with almost as much gain.

I have no test gear for 70cms
other than my FT817 and a power meter so I had to check the
antenna using these. The SWR meter on the FT817 suggested the
match was not brilliant (2 bars, which is about 2:1?) but not
bad. A quick test using the local repeater with the antenna
mounted vertically was successful and suggested some directionality.
So, the next stage was to get out on the Sunday morning with
the antenna and the 5W FT817 and see how it performed.

Results

A local highspot was chosen
for the contest. Highspot is a relative term as there are
few real hills in this part of the UK and this "bump"
behind the town of Newmarket QTH JO02DD is only around 30m ASL!
Fixing the antenna to the support "mast" and
trapping the mast in the car door, it was time to plug in the
FT817, turn
on and see what could be heard and worked.

The results were amazing. In
a few hours of operating, much of it in the rain and with distinctly
poor conditions a total of 10 stations in 8 locator squares
all across the country were worked all with just 5W SSB apart from the best contact
(which was on CW) with F8BRK
who was 326kms away in France. The site chosen was screened
towards France by trees and rising ground making this final contact
all the more pleasing. The contact started out on SSB but he
was struggling so I switched to CW so he could clearly get my
details.

Conclusions

Do give 432MHz SSB a go sometime
and if you think you have no suitable antenna then turn to your
wife or girlfriend's wardrobe and search out an old coat hanger.

If you only come on for the
odd contest you will be assured of some fun and who knows you
might be persuaded to erect a more permanent beam and rotator
and find out what the band is REALLY good for. Even if you can
only run a few watts of SSB and a small beam the band has lots
to offer especially in the smallest of lifts.